The present invention relates generally to cameras and, more particularly, to a system for mounting a camera lens.
The size of the image sensor array in video cameras such as web cameras has been shrinking due to improvements in technology. This leads to a decrease in the size of the sensor die on which the sensor is mounted. Based on optics principles, to maintain a field of view the lens must be moved closer to the image sensor die as the die size is reduced. In a typical lens mounting system, the user can adjust the relative position of the lens with respect to the sensor die by turning a focus ring. The same relative positioning is used for focusing and zooming operations. A problem arises that the user may bring the lens assembly in contact with the sensor die and unknowingly push the lens assembly against the sensor die, which may lead to the cracking of the lens or damage to the image sensor or other components of the lens mounting apparatus such as the pins connecting the image sensor to the substrate or PCB.
Embodiments of the present invention provide a lens mounting apparatus which allows the user to bring the lens assembly into full contact with the sensor or housing. A focus ring is typically provided for moving the lens assembly relative to the sensor. Once the lens assembly is in full contact with the sensor, further turning of the focus ring will cause the focus ring to slip relative to and ratchet with the lens housing, in a manner similar to a torque wrench, thus avoiding the application of excessive forces on and causing damage to the lens and other components of the lens mounting apparatus. Furthermore, a locating device is used to register the lens mounting apparatus to the sensor package. This is desirable because the decrease in size of the sensor reduces the allowable alignment tolerance between the lens and the sensor die from about 0.7 mm to less than 0.3 mm.
In accordance with an aspect of the present invention, a lens mounting apparatus for mounting a lens to a substrate having a sensor in a sensor housing mounted on the substrate comprises a lens mount member including a lens mount body coupled with the lens. The lens mount body includes a locating element configured to register the lens mount body to the sensor housing mounted on the substrate. The lens mount member includes a flexible mounting element configured to be attached to the substrate and permit movement of the lens mount body toward and away from the sensor housing.
In some embodiments, the locating element comprises a plurality of locating ribs configured to align the lens mount body with the sensor housing. The lens mount body is configured not to make contact with the substrate. The flexible mounting element comprises a pair of flexible mounting straps disposed on opposite sides of the lens mount body. The lens mount member is configured to maintain a gap between the sensor and the lens when the lens is in focus. The lens mount member includes a threaded portion to be threadingly coupled with the lens to permit adjustment of a position of the lens relative to the sensor.
In accordance with another aspect of the invention, a lens device comprises a lens disposed in a lens housing. The lens housing includes a coupling surface having a plurality of grooves. A lens mount member is threadingly coupled with the lens housing to permit adjustment of a position of the lens housing relative to the lens mount member. A focus ring includes a slip ring portion coupled with the coupling surface of the lens housing. The slip ring portion includes a plurality of teeth disposed on a flexible slip ring support and engaged with the grooves of the coupling surface to turn the lens housing to adjust the position of the lens in an axial direction relative to the lens mount member, between a fully extended position where the lens is farthest from the lens mount member and a fully retracted position where the lens is closest to the lens mount member. The flexible slip ring support permits the teeth to slip out of and ratchet with the grooves of the coupling surface when the focus ring is rotated in a direction to move the lens toward the lens mount member after the lens has reached the fully retracted position.
In some embodiments, the slip ring portion includes a pair of teeth disposed on opposite sides of the lens housing. The plurality of grooves of the coupling surface are outward facing grooves disposed on an external surface of the lens housing. The slip ring portion includes a plurality of inward facing teeth. The focus ring is movable in the axial direction toward and away from the lens mount member with the teeth of the slip ring portion of the focus ring engaged with the grooves of the coupling surface of the lens housing.